fix: code quality improvements across server, matcher, and proxy

[yesdevnull]

Summary

• Proxy shutdown timeout: Shutdown now splits timeout between capture drain and HTTP drain instead of blocking indefinitely on captures.Wait()
• Extract ReconstitutedBody helper: Eliminated triple-duplicated io.MultiReader + anonymous struct pattern into internal/httputil.ReconstitutedBody
• Typed body reader errors: lazyBodyReader returns typed error instead of bool, distinguishing I/O errors from body-too-large
• FilePath on MatchResult: Eliminated two O(n) linear scans per request by threading file path through the matcher via NewWithPaths
• Clear body_file errors: resolveBodyFile checks os.Stat before EvalSymlinks so missing files get "not found" instead of confusing symlink errors
• Template error logging: renderTemplate now logs a warning when template execution fails instead of silently returning raw template source
• Bounded proxy captures: Semaphore caps concurrent capture goroutines at 20; request fields are copied before spawning to avoid referencing *http.Request after handler returns

Test Plan

• All existing tests pass with -race flag
• golangci-lint run ./... — 0 issues
• go vet ./... — clean
• gofmt -l . — all formatted
• New tests added for each fix:
  • TestProxyShutdownRespectsTimeoutWithPendingCaptures
  • TestReconstitutedBody, TestReconstitutedBodyEmpty
  • TestMatchBodyIOError
  • TestMatchResultFilePath
  • TestServe_BodyFile_Missing_ClearLogMessage
  • TestServe_TemplateExecutionErrorLogged
  • TestProxyCapturesConcurrencyBounded

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR improves request matching, logging, proxy capture behavior, and shared HTTP body handling across the server/matcher/proxy components, with accompanying tests.

Changes:

• Thread coat source file paths through the matcher (MatchResult.FilePath + NewWithPaths) to avoid per-request scans and improve logging/body_file resolution behavior.
• Extract shared request-body “reconstitute” logic into internal/httputil.ReconstitutedBody and use it from server + matcher.
• Improve proxy shutdown/capture behavior (timeout split, bounded capture concurrency) and expand tests around logging and body_file/template behavior.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
internal/server/server.go	Uses matcher.NewWithPaths, logs template execution failures, resolves body_file using match file path, and adopts httputil.ReconstitutedBody.
internal/server/server_test.go	Updates body_file ambiguity expectations and adds new tests for clearer missing-file logs and template execution warning logging.
internal/server/verbose_test.go	Updates verbose logging expectations now that MatchResult.FilePath is always available.
internal/proxy/proxy.go	Adds capture semaphore, copies request fields before spawning capture goroutines, and splits shutdown timeout between capture drain and HTTP drain.
internal/proxy/proxy_test.go	Adds tests intended to cover bounded capture concurrency and shutdown timeout behavior.
internal/matcher/matcher.go	Adds MatchResult.FilePath, NewWithPaths, typed body read errors, and uses httputil.ReconstitutedBody.
internal/matcher/matcher_test.go	Adds tests for body I/O error handling and FilePath propagation.
internal/httputil/body.go	Introduces ReconstitutedBody helper.
internal/httputil/body_test.go	Adds unit tests for ReconstitutedBody.

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[Copilot]

Pull request overview

This PR improves request matching, server response handling, and proxy capture robustness by reducing duplicated body-reconstitution code, propagating coat source paths through the matcher, and tightening shutdown/capture behavior.

Changes:

• Thread coat source FilePath through matcher.MatchResult via matcher.NewWithPaths, removing per-request scans in the server.
• Extract shared request-body reconstruction into internal/httputil.ReconstitutedBody and use it from server + matcher.
• Improve operational behavior: proxy shutdown now bounds time spent waiting on captures; proxy capture uses a semaphore and copies request fields before async capture; server logs template execution failures and clarifies body_file errors.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
internal/server/server.go	Uses NewWithPaths/MatchResult.FilePath, factors body reconstitution, logs template exec failures, refines body_file resolution.
internal/server/server_test.go	Updates/extends tests for duplicate coats behavior, clearer body_file errors, and template exec warning logging.
internal/server/verbose_test.go	Updates verbose logging expectations for duplicate coats to log the first coat’s file path deterministically.
internal/matcher/matcher.go	Adds NewWithPaths, propagates FilePath into MatchResult, and returns typed body-read errors while restoring request bodies.
internal/matcher/matcher_test.go	Adds coverage for body I/O errors and MatchResult.FilePath propagation.
internal/proxy/proxy.go	Bounds concurrent capture work with a semaphore, copies request fields for async capture, and splits shutdown timeout between capture drain and HTTP drain.
internal/proxy/proxy_test.go	Adds tests for bounded-capture behavior under load and shutdown returning within a bounded time.
internal/httputil/body.go	Introduces ReconstitutedBody helper for replaying captured bytes + delegating Close to the original body.
internal/httputil/body_test.go	Adds unit tests for ReconstitutedBody behavior with captured bytes and empty capture.

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